Ukraine's defense minister confirmed Monday that an AN-26 transport plane had been downed near the separatist stronghold of Luhansk on the Russian border and said the missile that hit it must have been fired from Russian territory.

"Defense Minister Valeriy Heletei reported to Ukrainian President Petro Poroshenko that the crew of the AN-26 ... was shot down," the Ukrinform news agency said, citing the presidential press service. It said crew members had survived and made contact with the General Staff in Kiev, the capital, although it was unclear from the reports whether all eight people on board survived.

Heletei said the plane was hit at an altitude of 21,450 feet, which he said is far beyond the range of any mobile rocket launchers that the pro-Russia separatists are known to have in their arsenal.

"The plane was hit by another, more powerful missile that was probably used from the territory of the Russian Federation," the press service said Heletei told a meeting of Ukrainian security officials.

Neither Russian President Vladimir Putin, who is on a tour of Latin America, nor major Russian state-run media responded to the accusation.

Sergei Chuzavkov / Associated Press

Ukrainians in Kiev on Monday protest France's sale of amphibious assault ships to Russia, which the demonstrators oppose because Russia backs separatists fighting in eastern Ukraine.

Separatists claimed responsibility for the plane's downing and a Kyiv Post editor said via Twitter that four of the crew members had been taken prisoner and were being interrogated by militants in the town of Krasnodon, a city in the Luhansk region still in militant hands.

Kiev's claim that the missile was fired from Russian territory followed an accusation from Moscow a day earlier that Ukrainian forces had fired a shell across the border into Russia's Rostov region, killing a man. The Russian Foreign Ministry warned in a statement of "irreversible consequences" for acts of aggression against its territory.

Ukraine's worst unrest since the 1991 collapse of the Soviet Union was sparked by former President Viktor Yanukovich's decision to scrap a deal with the European Union in favor of closer ties with Russia.

A spokesman for Ukraine's National Security and Defense Council, Andriy Lysenko, said the incident was probably an accidental firing by pro-Russia militants who ferry weapons and reinforcements across that part of the border.

Fighting in the eastern Ukraine regions of Donetsk and Luhansk has intensified since government troops recaptured the militant stronghold of Slovyansk on July 5, driving the separatists to flee to the two main cities and regroup for the battle to keep the territory they hold.

The government offensive was relaunched June 30 after a 10-day unilateral cease-fire failed to convince the militants that they should lay down their arms and negotiate their grievances. The resurgent Ukrainian troops have since recovered about half of the eastern territory seized by the separatists in the spring.